Is Drinking Too Much Water Really Dangerous?

Yes. The average person’s kidneys can rid the body of nearly a quart of water per hour. But if you consume extremely large quantities of fluids, exceeding the kidneys’ ability to excrete them, you can drink to excess.

Water overload, or hyponatremia, is a rare condition seen almost exclusively in marathon runners and ultra-endurance athletes when they drink too much fluid and lose excessive sodium through sweat. This combination dilutes the sodium concentration in the blood, causing a potentially lethal condition that starts with symptoms like headache, confusion, vomiting, and fatigue. If severe enough, hyponatremia can lead to seizures, coma, and even death, but it usually requires three to four hours of fairly continuous exercise and continuous consumption of fluids.